Any bike manufactured before 1986 only needs EITHER a front or rear switch, not both.
But personally, I think the use of either brake should go through a switch, it's basic safety common sense.
4.3.2. Switching
Motorcycles first used on or after 1 April 1986 must have a stop lamp that switch on from both brake controls. However, a small number of motorcycles first used from this date were approved with the stop lamp switching on by only one control